Foucault's Pendulum

Casaubon, Jacopo Belbo, and Diotallevi, editors at a Milan vanity press worn down by years of manuscripts from occultists they privately call the Diabolicals, start feeding real historical fragments, the Templars, the Rosicrucians, ley lines, the forged Protocols of the Elders of Zion, into a random-connection generator purely as parody. Eco's actual target isn't the occult but the mental habit underneath it, the refusal to let any two facts stay unconnected, a habit the editors indulge for sport and then watch metastasize into something that believes itself.

Foucault's Pendulum itself, hanging in Paris's Conservatoire des Arts et Métiers exactly where the physicist Léon Foucault installed it in 1851 to demonstrate the earth's rotation, is the one fixed point in a novel otherwise devoted to interpretations that spin freely around any fact you hand them. Eco stages the climax directly beneath it because it is the single object in the book that means only what it demonstrates, no matter how badly the conspiratorial mind wants it to mean anything more.

Diotallevi, the group's Kabbalist and the third of the three editors, develops cancer partway through the game and comes to read his own illness as the Plan's first real retribution, insisting that fabricating sacred meaning where none exists is itself a transgression the universe will eventually answer. Eco lets his slow death run alongside Belbo's unraveling as the novel's quietest argument that the parody was never entirely costless, even for the one editor who had treated it, until his diagnosis, as pure intellectual sport rather than anything requiring belief.

Years before the editors invent their game, an occultist calling himself Colonel Ardenti brings them a supposed decoded medieval Templar message and then vanishes, possibly murdered for it. Eco lets that earlier, half-real episode supply the raw material Belbo's later invention cannibalizes, deliberately blurring the line between what the editors are making up and what may already have gotten someone killed before the novel even begins.

The editors name their random-connection-generating computer program after the medieval Kabbalist Abraham Abulafia, and let it manufacture apparent significance out of pure noise, any two facts fed in will produce a plausible-sounding link. Writing in the mid-1980s, Eco anticipates with unsettling precision how algorithmic pattern-matching would later manufacture belief at internet scale, decades before search engines made exactly this kind of manufactured connection ordinary.